1. Field of the Invention
The present invention relates to a particulate matter detection device. In particular, it relates to a particulate matter detection device that detects a concentration of particulate matter of exhaust emitted from an internal combustion engine.
2. Related Art
Conventionally, a particulate matter detection device has been provided in the exhaust pipe of an internal combustion engine for detecting a concentration of particulate matter (hereinafter also referred to as PM) in exhaust. For example, a particulate matter detection device has been disclosed, in which a particulate matter detection electrode is configured from a porous electrically conductive material having a predetermined electrical resistance value, that detects an amount of particulate matter in exhaust by measuring a change in an electrical resistance value brought about by particulate matter adhering to this detection electrode (refer to Japanese Unexamined Patent Application, Publication No. 2006-266961).
In addition, a PM emission detection device has been disclosed that can continuously detect a PM amount in exhaust by sequentially regenerating a PM sensor, and detecting a PM amount in exhaust by way of a PM sensor other than the PM sensor undergoing regeneration (refer to Japanese Unexamined Patent Application, Publication No. 2008-190502). This PM sensor has an insulated structure in which electrodes are disposed alternately, and a PM amount in exhaust is detected based on an output value (current value) of the PM sensor by adopting a property in that the electrical resistance value becomes small due to PM conducting when adhering and depositing on the electrode (refer to Japanese Unexamined Patent Application, Publication No. 2008-190502).
In addition, a particulate matter detection device has been disclosed that is mounted in an exhaust pipe, and measures an electrical characteristic of an electrode unit after particulate matter in the exhaust has adhered to the electrode unit by applying a predetermined voltage to the electrode unit, and detects the amount (concentration) of particulate matter in the exhaust from the electrical characteristic thus measured (refer to Japanese Unexamined Patent Application, Publication No. 2008-139294).